Short wave radio apparatus



Aug. 26, 1941. ofE. DOW- I SHORT WAVE vRADIO APPARATUS Filed Nov. 3, 1939 "BIN AAAAA vvvvv am new m EI SY I NV EN TOR.

ORV/L E. now I M ATTQRNEY.

Patented Au as, 1941 UNITED STATE snon'r wavn namo mmarus Orville E. Dow, PortJeflerson, N. Y.,'assignor to Radio Corporation of Delaware America, a corporation of Application November 3, 1939, Serial No. 302,655 r The present invention relates to electron discharge device circuits, and particularly to such circuits for use with ultra short radio waves.

One of the objects of the present invention is to provide an emcient frequency multiplier circult for use at frequencies below two meters.

Another object is to provide an electron disj charge device multiplier circuit which will ediciently triple the irequency of the input waves to frequencies of the order of 450 megaoycles and higher.

A further object is to provide a push-pull type of electron discharge device frequency multiplier for use at ultra short waves, whose anode, cathode and control electrodes are individually coupled totuned circuits, so arranged as to accentuate the desired harmonic component to be obtained from the output at the multiplier.

lilac foregoing hjects and others which will appear from a reading of the following descrlp tion are achieved in accordance with .one embodiment of the invention by the use of a frequency multiplier consisting of a pair of ultra high ireouency electron discharge devices connected in push-pull relation. The control electrodes oi both devices are so connected together that at the input or fundamental frequency there is a high imance from control electrode to control electrode, while at the third harmonic of the inpu frequency there is a low impedance from control electrode to control electrode. The fila- '(ci. ass-sci two terminals or-leads tor-each anode and ri and a center tap to the'fllament. Such devices are known in the art, one product being sold by the RCA Manufacturing Company, Inc, under the trade symbol i i-2074.

The anodes of vacuum tubes iii, 32 are interconnected by means of a pair of tuned circuits,

I03 and Ill, extending from opposite sides of the envelope. Tuned circuit its is coupled to one set of anode leads, while tuned circuit iii is coupled to the other set of anode leads. Circult I03 comprises a pair of iecher wires tuned by means of a sliding bridge GM and connected intents of both devices are soconnected that there is a low impedance from one filament to the other at the third harmonic, while the anodes are so connected that there is a. high ance irom 5 oneenode to the other anode at this same harmonic. In this way I have been able to accentuate the desired harmonic component to be derived from the multiplier. In the circuit actuvelopel The ally tried out in practice, two triode vacuum tubes were employed, and iecher wire systems oi predetermined-leng hs were used in both anode and circuits to obtain the desired control electrode impedance relations.

[A more detailed description .of the invention follows in conjunction with a drawing whose sin;- gle figure shows the frequency multiplier system oitheinvention used by way of example only m an ultra short wave transmitter.

Referring to the drawing in more detail, the

multiplier is shown as consisting of a p oi electron discharge device triodes SM and ltd, each of which has a grid G. a filament I and located within an evacuated enan anode A triodes are 0! a type which have together at the ends remote from the tubes by means of a bar I20 to whose center is supplied a potential which is positive relative to the illsmeat, as shown. Circuit iii is also composed oi a pair of lecher wires in each of which is an air condenser H0. Both circuits lot and iii are resonant to the third harmonic frequency, hence are high impedance circuits at this third harmonic. The lengths of circuits Hi and H33 are shown difl'erent because the capacities of tho circuits are diflerent. In. each case the lumped capacities are a minimum. The capacity across tuned circuit tilt iscomprised oi the-plate to grid capacities of the tubes it! tilt in series. This capacity is much larger than the lumped capacity across tuned circuit Hi, which is only the stray capacity between the two plates -of condensers H6 which are connected in circuit with i H. A suitable output or utilisation circuit to be described 'later'is coupled to tuned circuit iii.

The grids G; G are also connected to two circults i0! andiiit. The circuit 8% includes an inductance coil 5 and a tuning air condenser we and is known as theiundamental circuit, to which is coupled an input circuit having waves of th frequency to be multiplied. A grid bias resistor us connects the electrical center of coil M5 to ground. The circuit lot is known as the harmonic circuit and consists oi a section of twoconductor transmission line connected at one end to the grids and open at the other end. The electrical length of this line it? is adjustable by means or the telescoping tubular conductors from which it is made, as shown. and is adiustm to be about one-quarter wavelength longior the third harmonic frequency, so that the impedance from the grid of one vacuum tube to the grid of the other vacuum tube is very low at this harmonic irequency, Itwill be noted that harmonic circuit I01 also influences the oi the grid circuit at the {undamental frequency. condenser I86 power units.

RCA 829 or 832 type whichis known in the art has little effect on the tuning of the harmonic circuit- IIII since the condenser is located at the low impedance point of circuit I01. Whethercondenser III! is mounted on the left or the right of the tubes IIII, I02, itsaction on circuit III! is small since a third harmonic voltage nodal point on circuit I01 15- located at the grids. At

the fundamentai'frequency, i..e., the. input frequency, the impedance of circuit IIII as it appears across the grids G, G is a capacity reactance. This capacitance is added in parallel with the condenser m, which together with the electrode capacitance tunes circuit III so that ther is a high impedance from the grid of tube III to the grid of tube III at the fundamental frequency.

The filament leads for each of the vacuum tubes IIII III! are separately enclosed in a tubular conductor from which they are insulated, the tufilament F of the other vacuum tube is very low at the harmonic frequency. Heating energy for the filamentsis supplied to the filament leads at the ends remote from the vacuum tubes, near bridging conductor I".

The input circuit providing the'energy-of the frequency to be multiplied, i. e., the fundamental so far as the multiplier is concerned, is shown as a radio frequency amplifier stage III comprising an electrondischarge device of the push-pull beam power type. This stage is a heater-cathode type containing in a single envelope two beam Such an amplifier may be of. the

as being a balanced and compact structure of beam power units, having the desirable characteristics of internal shielding, 'close electrode spacing, and short and heavy internal leads.

Since the amplifier tube, per-se, forms no part' of the present invention, it is not believed necessary to describe the same in any greater detail.

. The output circuit of the amplifier stage, labeled I I8, is conductively coupled by .wayof blocking condensers. II| to the inductance coil H5 of tuned circuit I05 of the multiplier stage. The required mutual inductance is obtained by tapping down on the output tuning inductance of the amplifier. ."I'he coefiicient of coupling and the Justed by shorting bridge. I until the inductance tunes the anode capacity and results in a high impedance from anode to anode at the harmonic frequency. The voltage developed across the anode circuit is coupled by means of condensers IIII into circuit III which is resonant to the third harmonic frequency. The band pass response of this coupled circuit is determined by the coefilcient-of coupling and the damping of the circuits. The coefiicient of coupling is varied by adjusting condensers III and the damping is varied by changing the tapping point of the outputload oncircuit I I I. Duetothe high impedance from grid to grid at the fundamental frequency a high voltageappears across the grids. The im: pedance at the fundamental frequency from filament to filament is a low inductive reactance so there is also a high voltage from grid to filament of each tube. This excitation resultsin rectified grid current fiowing to ground through resistor Ill and establishes the required grid. bias. This bias ishigh enough so that the electrons flow in short pulses from thefilamentto the anode of each'vacuum tube, which anode is maintained at a positive potential.v This. short current pulse can beconsidered as consisting of many simple harmonic components the frequencies of which are multiples of the input frequency. The shape of this short current pulse can be changed by adjusting excitation voltage and grid bias so that a particular component, say the third harmonic,

will be accentuated- As electrons travel from the filament to the anode, charges will be induced on the filament, grid and anode. If the impedances of the circuits connected to the various electrodes are high the induced charges will result in high induced voltages. These induced. voltages on the electrodes will alter the velocity of the electrons in the current pulse and thereby change the shape of the pulse. By making the impedance from grid to grid and filament to 3 filament low at the desired harmonic (third) frequency; the current pulse will arrive at the anode with the desired harmonic component still accentuatedand deliver its energy to the output circuit.

'- It is possible to further increase the harmonic I output by adjusting harmonic circuit IIII so that loading is adiusted'to obtain the desired band 7 pass characteristics, in known manner.

For deriving! output .energy of the desired a harmonic from the multiplier Ill, I02, there is provided a loop circuit II9 whose legs are connected at their ends to suitable points on the conductcrs of tuned circuit I I I. 4- coaxial transmission line TL extending to a suitable load, such as an antenna, not shown, has'its outer conductor grounded and its inner conductor coupled to a point on one leg of the loop III which point is closer to one conductor of timed circuit YIII than to the other. conductor of III by a distance which is equal to one-half wavelength at the third harmonic frequency. This mode of cou- Pling the single coaxial line TL to the loop' Ill symmetrical loading of the balanced cir- In the operation of the system of the invention, the length of the lecher pair I08 is ad-- the impedance across the grids is of such value as to permit regenerative voltage to be fed back from the anode to the grid of each vacuum tube. since the coupling between the anodes and grids is capacitive the impedance from grid to grid at the harmonic frequency would be inductive. This would be obtained by making I" slightly longer than a quarter wave atrtheharmonic frequency. This increase in power output is obtained at a sacrifice in band width. More specifically, the impedance of'circuit III! is raised high enough to build up a voltage (of desired harmonic frequency) on the grids due to the current flowing in the plate to grid capacity. Re-

generation can also be accomplished by leaving the impedance of III from grid to .srid zero or very low and making the impedance from filament to filament capacitive (for desired harmonic frequency) and of sufiicient value to build up the required regenerative voltage due to the current fiowing through the plate to filament ca- .pacity. In either case the amount of regeneraamplifier stage H8 consisted of a frequency tripler, RCA-832 type of tube, functioning tov and the tubes MI and I02 were triodes of the RCA A-2074 type. and the transmitter circuit preceding the push-pull multiplier of the invention was of a type generally disclosed in my copending application Serial No. 282,406, filed July 1, 1929.

What is claimed is:

1. An electron discharge device comprising a impedance at the desired harmonic arranged in parallel to said last high impedance circuit for delivering output energy from said device, said other circuit being resonant at the desired harmonic and having adjustable means therein for varying the coefllcient of coupling between said device and the output circuit to which it is coupled. 1

5. A frequency multiplier comprising a pair of electron discharge devices each having a cathode, an input electrodeand an output electrode,

cathode, an input electrode and an output elec trode, a first circuit of high impedance at the fundamental frequency coupled between said input electrode and a point of fixed alternating current potential, and a second circuit tuned to another frequency also coupled to said input electrode, said last frequency being such that the quotient of the larger of the said two frequencies'divided by the smaller of the said two frequencies is an integer, a'third tuned circuit coupled between said cathode and a point of fixed alternating current potential, and a circuit of high impedance at said other frequency coupled to said output electrode, said second and third tuned circuits being tuned to provide correct impedance for the production of waves of said other frequency.

2. A frequency multiplier comprising an electron discharge device having a cathode, an input electrode and an output electrode, a first circuit tuned to the fundamental frequency coupled between said input electrode and a point of fixed a. pair of tuned circuits coupling said input electrodes together, one of said tuned circuits being a high impedance at the fundamental frequency and the other of said tuned circuits being a low im 2-. m at the desired harmonic, and a pair of circuits both of high impedance at the desired harmonic coupling said output electrodes togather, and a circuit of low impedance at the desired harmonic coupling said cathodes to gether.

6. A frequency multiplier comprising a pair of electron discharge devices each having a cathode, an input electrode and an output electrode, a pair of tuned circuitscoupling said input elecallel relation, a pair of tuned circuits in parallel relation coupling said output electrodes together,

alternating current potential, and a second circuitv tuned to the desired harmonic frequency also coupled to said input electrode, a third tuned circuit coupled between said cathode and a point of fixed alternating current potential, and a circuit of high impedance tuned to the desired harmonic of said fundamental coupled between'said output electrode and said point of fixed alternating current potential.

3. A frequency multiplier; comprising an electron discharge device having a cathode, an input electrode and an output electrode, a circuit of high impedance at the fundamental frequency coupled between said input electrode and a point of fixed alternating current potential, and. a circuit tunedto the desiredharmonic also coupled to said input electrode, a circuit of low impedance at said desired harmonic coupled between said cathode and a point of fixed alternating current potential, and a circuit of high impedput electrode and an output electrode, a circuit of high impedance at the fundamental frequency coupled between said input electrode add a point of ,fixed alternating current potential, and a circuit of low impedance at the desired harmonic also coupled to said input electrode, a circuit of low impedance at said desired harmonic coupled between said cathode and a point of fixed alternating current potential, and a circuit of high impedance at the desiredharmonic coupled between said anode and a point of fixed alternatand a tuned circuit coupling said cathodes together, said circuits being tuned to augment the generation of harmonic energy.

7. A frequency multiplier comprising a pair of electron discharge devices each having a cathode, an input electrode andan output electrode, a pair of tuned circuits coupling said input electrodes together, one of said tuned circuits being a high impedance at the fundamental frequency a and the other of said tuned circuits being a low impedance at the desired harmonic, and a circuit of high impedance at the desired harmonic coupling said output electrodes together, ands. circuit of low impedance at the desired harmonic coupling said cathodes together,

8. A frequency multiplier comprisinga pair of electron discharge devices each having ,a filament, 2. grid and-an anode, means providing a high impedance at the fundamental frequency and a low impedance at the desired harmonic frequency between said grids, adjustable means providing a low impedance at the desired harmonic frequency between said filaments, a pair,

of tuned circuits each coupled between said anodes, said pair of tuned circuits providing a high impedance at said desired harmonic frequency, .and an output circuit coupled to one of said pair of tuned circuits.

9. A frequency tripler comprising a pair of electron discharge devices each having a filament, an input electrode and an output electrode, a parallel circuit of inductance coil and "condenser and tuned to-the fundamental frequency coupled between said input electrodes,

means connected to said coil for providing a bias for said input electrodes, a lecher wire system substantially one-quarter of a wavelength long at the'third harmonic frequency coupled in parallel to said parallel circuit, a pair of lecher conductor systems resonant at the third harmonic ing current potential, and another circuitof high frequency coupled between said output electrodes, one of said last lecher conductor systems having in series with each conductor thereof an adiustable condenser, and a tunedv circuit between said filaments of such dimensions as to render the impedancebetween said filaments very low at the third harmonic frequency.

10. A frequency tripler comprising a pair of electron discharge devices each having a filament, an input electrode and an output electrode, a parallel circuit of inductance coil and condenser and tuned to the fundamental freof electrodestructures, each structure including an input electrode, an output electrode and a harmonic frequency coupled between said output electrodes, one of said last lecher conductor systems having in series with each conductor thereof an adjustable condenser, and a tuned circuit between said filaments comprising a tubular conductor surrounding the-leads and individual to each filament, and a shorting bar across said tubular conductors, the distance between said bar-and the active portion of each filament being one-half wavelength at the third harmonic.

11. An electron discharge device comprising av cathode. an input electrode and an output electrode, a first circuit of high impedance at the fundamental frequency' coupled between said input electrode and a point of fixed alternating filament, a pair of tuned circuits coupling said input electrodes together, said tuned circuits being in parallel relation, a pair of tuned circuits in-parallel relation coupling said output electrodes together, and a tuned circuit coupling said filaments together, said circuits being tuned to augment the generation of harmonic energy.

13. An ultra short wave frequency multiplier comprising an electron discharge device having a filament, a grid and an anode, an input'circuit tuned 'to a fundamental frequency coupled between said grid and filament, a circuit substantially eifectively one-quarter wavelength long for the desired harmonic frequency connected at its low impedance terminal to said grid, a

circuit tuned to the desired harmonic coupled between said anode and ground, and a circuit tuned to augment the generation of harmonic energy coupled between said filament and ground.

14. Anultra short wave frequency multiplier comprising an electron discharge device having a filament, a grid and an anode, an input circuit tuned to a fundamental frequency coupled between said grid and filament, a circuit substanr tially eifectively one-quarter, wavelength long for current potential, and a second circuit tuned to a harmonic of the fundamental frequency also coupled to said input electrode, a third tuned circuit coupled between said cathode and a point a onvmn a; now. 

